Rollup merge of #106557 - Ezrashaw:ui-test-fixups-1, r=GuillaumeGomez

Add some UI tests and reword error-code docs

Added UI tests for `E0013` and `E0015`. Error code docs for `E0015` were a bit unclear (they referred to all non-const errors in const context, when only non-const functions applied), so I touched them up a bit.

I also fixed up some issues in the new `error_codes.rs` tidy check (linked #106341), that I overlooked previously.

r? ``@GuillaumeGomez``

4 files changed, 34 insertions, 0 deletions

diff --git a/src/test/ui/error-codes/E0013.rs b/src/test/ui/error-codes/E0013.rs
new file mode 100644
index 00000000000..9b3982a785b
--- /dev/null
+++ b/src/test/ui/error-codes/E0013.rs
@@ -0,0 +1,4 @@
+static X: i32 = 42;
+const Y: i32 = X; //~ ERROR constants cannot refer to statics [E0013]
+
+fn main() {}
diff --git a/src/test/ui/error-codes/E0013.stderr b/src/test/ui/error-codes/E0013.stderr
new file mode 100644
index 00000000000..dc22053a638
--- /dev/null
+++ b/src/test/ui/error-codes/E0013.stderr
@@ -0,0 +1,11 @@
+error[E0013]: constants cannot refer to statics
+  --> $DIR/E0013.rs:2:16
+   |
+LL | const Y: i32 = X;
+   |                ^
+   |
+   = help: consider extracting the value of the `static` to a `const`, and referring to that
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0013`.
diff --git a/src/test/ui/error-codes/E0015.rs b/src/test/ui/error-codes/E0015.rs
new file mode 100644
index 00000000000..b0211358d81
--- /dev/null
+++ b/src/test/ui/error-codes/E0015.rs
@@ -0,0 +1,8 @@
+fn create_some() -> Option<u8> {
+    Some(1)
+}
+
+const FOO: Option<u8> = create_some();
+//~^ ERROR cannot call non-const fn `create_some` in constants [E0015]
+
+fn main() {}
diff --git a/src/test/ui/error-codes/E0015.stderr b/src/test/ui/error-codes/E0015.stderr
new file mode 100644
index 00000000000..ec1ce47b2ce
--- /dev/null
+++ b/src/test/ui/error-codes/E0015.stderr
@@ -0,0 +1,11 @@
+error[E0015]: cannot call non-const fn `create_some` in constants
+  --> $DIR/E0015.rs:5:25
+   |
+LL | const FOO: Option<u8> = create_some();
+   |                         ^^^^^^^^^^^^^
+   |
+   = note: calls in constants are limited to constant functions, tuple structs and tuple variants
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0015`.